The apps disappeared yesterday, not too long after the announcement of Telegram X, a faster experimental client for the encrypted messenger service.

The absence from the App Store search result was first spotted by reddit users.

The reason? The Telegram apps appear to have fallen foul to Apple's strict content rules which impose some kind of filtering. Telegram's CEO, Pavel Durov explained in a tweet that Apple received reports of "inappropriate content [...] made available" to Telegram users.

We were alerted by Apple that inappropriate content was made available to our users and both apps were taken off the App Store. Once we have protections in place we expect the apps to be back on the App Store.

What content was deemed inappropriate by Apple is still unclear, but the CEO remains confident that the app will be reinstated shortly:

Once we have protections in place we expect the apps to be back on the App Store. - Pavel Durov

Apple's guidelines for iOS developers include a section specific to apps that contain user-generated content - a wide category where messaging apps are -. This policy requires that apps include:

A method for filtering objectionable material from being posted to the app

A mechanism to report offensive content and timely responses to concerns

The ability to block abusive users from the service

Published contact information so users can easily reach you

When Telegram was created in 2013, it was one of the only apps for encrypted messaging. Other messengers followed suite by adding encryption features - often based upon Signal protocols - much later.
But Telegram is no ordinary messaging app. Even though today it is the most used app for ICO and crypto-currency groups (with Slack coming second), Telegram is often associated by the media with terrorist groups.

But Telegram will be trying to shed this image and become instead a cryptocurrency-based network. According to several sources, Telegrams plans to launch its own ICO, with a plan to raise $1.2BN to fund a metamorphosis from a simple messaging apps to a crypto-currency powered network able to run applications on its blockchain, in the style of Ethereum.